Mother’s Childhood Might Affect Children’s Memory

Researchers studied the brain function of pre-adolescent mice that have a genetically-created defect in memory. When these young mice were given an enriched environment, which is exposure to stimulatory objects, enhanced social interaction and voluntary exercise for two weeks, the memory defect, caused by inhibiting the formation of Ras-GRF1 and Ras-GRF2 proteins, was reversed.

After a few months, the same mice were fertilized and they gave birth to offspring that had the same genetic mutation. However, the offspring had no indications of the memory defect even though the offspring were never exposed to an enriched environment like their mothers. “What is so unique about this study is that we provided an enriched environment during pre-adolescence, months before the mice became pregnant, yet the beneficial effect reached into the next generation,” said Dean Hartley, study co-investigator. “The offspring had improved memory even without an enriched environment.”

To prove that that improved memory of the offspring was not the result of better nurturing by mothers who were enriched when they were young, a number of offspring were raised by non-enriched foster mothers. Even in the offspring raised by non-enriched mothers, they still maintained an improved memory.

"This example of ‘inheritance of acquired characters’ was first proposed by Jean- Baptiste Lamarck in the early 1800s. However, it is incompatible with classical Mendelian genetics, which states that we inherit qualities from our parents through specific DNA sequences they inherited from their parents. We now refer to this type of inheritance as epigenetics, which involves environmentally-induced changes in the structure of DNA and the chromosomes in which DNA resides that are passed on to offspring,” said Larry Feig, PhD, professor of biochemistry at Tufts University School of Medicine.

The phenomenon described in this study indicates that juvenile enrichment affects learning and memory in the next generation. However, the study found that it does not in subsequent generations because the effect of the enriched environment wears off faster in the offspring.